The Void took the Vrykul, who were big and strong, and made them tiny and weak. That’s how we got Humans.
The Void took the Kobold, who were tiny and weak, and made them big and strong. That’s how we get Swolbolds.
And yes, Swolbold is the technical term for those big muscular Kobolds. I would have preferred Musclebold but what it is is what it is.